In recent years, multiple telephone station apparatus has become prevalent. Connection of several telephone station apparatus to one telephone line, facilitating positioning an extension telephone in several locations for convenience of use, has dramatically increased. One type of telephone station for use in connection with telephone lines comprises a pulse output type telephone station. Such devices may take the form of rotary dial mechanisms or a push-button dial assembly for keying the telephone to produce pulse outputs corresponding to the number dialed. The pulse outputs occur through interruption of a d.c. line voltage supplied through the telephone line to the telephone station. Each number (1-9) is dialed by producing a corresponding number of interruptions of the d.c. line, with zero produced by ten interruptions of the d.c. line voltage.
The use of more than one telephone station apparatus or hand set on a single pair of lines may create a problem known as "ring tap". Ring tap occurs on a phone during the dialing or keying of another, pulse output type phone connected to the same telephone lines. This causes the additional phones or extensions connected to the same lines to receive the dial pulses, thereby undesirably actuating the ringer of the other on-hook phones. It would be desirable to eliminate the ring tap that is caused in on-hook telephones, during dialing of another phone connected to the same telephone lines.
One approach to solving the ring tap problem has been the mechanical adjustment of a mechanical ringer used to signal the transmission of an incoming call, such as mechanical adjustment of the ringer or hammer. Such compensation for the ringer tap problem has not been completely satisfactory. Critical space adjustment is often necessary which necessitates increased production quality control to assure effective elimination of the ring tap problem. Increased quality control to assure elimination of ring tap, increases the cost of the telephone station apparatus.
In addition, mechanical adjustments of relative distance of movement and space between the ringer hammer and bells have been satisfactory only when used with dual bell ringer systems. This is due to the fact that the dual bell system allows slower relative movement of the hammer to produce the well-recognized ringing of the telephone station apparatus.
Mechanical adjustments to correct the ring tap problem in single bell ringer systems have not been successful, e.g., because a less rigid ringer hammer is used in order to allow faster movement to produce the well-recognized ringing sound. This lower ridigity in a single bell system makes proper mechanical adjustment difficult if the well-recognized ringing sound is to be produced.
Since the use of a dual bell ringer unduly increases the cost of the telephone station apparatus due to redundancy of components, it would be desirable to eliminate ring tap in single bell telephone systems, while still providing the well-recognized ringing sound.
It would also be highly desirable to be able to eliminate the ring tap problem in both single and dual bell ringer systems without requiring mechanical adjustment of the ringer pendulum and without substantially increasing the cost of the telephone station apparatus.